Chapter 15, Problem 3P

One of the main lessons of this chapter is that several bacterial genes are often transcribed from a single promoter into a large multigene (polycistronic) transcript. The region of DNA containing the set of genes that are cotranscribed, along with all of the regulatory elements that control the expression of these genes, is called an operon.

a. Which of the mechanisms in the following list could explain differences in the levels of the mRNAs for different operons?

b. Which of the mechanisms in the following list could explain differences in the levels of the protein products of different genes in the same operon? i. Different promoters might have different DNA sequences. ii. Different promoters might be recognized by different types of RNA polymerase. iii. The secondary structures of mRNAs might differ so as to influence the rate at which they are degraded by ribonucleases. iv. In an operon, some genes are farther away from the promoter than other genes. v. The translational initiation sequences at the beginning of different open reading frames in an operon might result in different efficiencies of translation. vi. Proteins encoded by different genes in an operon might have different stabilities.